The present invention relates generally to model-based predictive control of temperatures. More specifically, the invention relates to model-based predictive temperature control of steam in relation to inter-stage attemperation, which may be used in heat recovery steam generation (HRSG) systems in combined cycle power generation applications.
HRSG systems may produce steam with very high exhaust temperatures. In particular, HRSG systems may include superheaters through which steam may be superheated before being used by a steam turbine. If the exhaust steam from the superheaters reaches high enough temperatures, the steam turbine, as well as other equipment downstream of the HRSG, may be adversely affected. For instance, high cyclic thermal stress in the steam piping and steam turbine may eventually lead to shortened life cycles. Conventional control systems have been devised to help monitor and control the temperature of exhaust steam from HRSG systems. Unfortunately, these control systems often allow temperature overshoot during transient periods where, for instance, inlet temperatures into the superheaters increase rapidly. In addition, these control systems often require a great deal of tuning and re-tuning.